import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';

// class Square extends React.Component {
//   constructor(props) {
//     /**
//      * 在 JavaScript class 中，每次你定义其 子类 的构造函数时，都需要调用 super 方法。
//      * 因此，在所有含有构造函数的的 React 组件中，构造函数必须以 super(props) 开头。
//     */
//     super(props);
//     this.state = {
//       value: null
//     };
//   }

//   render() {
//     return (
//       <button 
//         className="square" 
//         onClick={ () => this.props.onClick() }
//       >
//         { this.props.value }
//       </button>
//     );
//   }
// }

/**
 * 如果你想写的组件只包含一个 render 方法，并且不包含 state，那么使用函数组件就会更简单
*/
function Square(props) {
  return (
    <button 
      className="square" 
      onClick={ props.onClick }
    >
      { props.value }
    </button>
  )
}

class Board extends React.Component {
  // constructor(props) {
  //   super(props);
  //   this.state = {
  //     squares: Array(9).fill(null),
  //     xIsNext: true
  //   }
  // }

  // handleClick(i) {
  //   /**
  //    * 使用 .slice() 方法创建了数组的一个副本，而不是直接修改现有的数组
  //   */
  //   const history = this.state.history;
  //   const current = history[history.length - 1];
  //   const squares = current.squares.slice();
  //   if(calculateWinner(squares) || squares[i]) {
  //     return;
  //   }
  //   squares[i] = this.state.xIsNext ? 'X' : 'O';
  //   this.setState({ 
  //     history: history.concat([{
  //       squares: squares,
  //     }]),
  //     xIsNext: !this.state.xIsNext
  //   });
  // }
  
  renderSquare(i) {
    return (
      <Square 
        value={ this.props.squares[i] } 
        onClick={ () => this.props.onClick(i) }
      />
    );
  }

  render() {
    // const status = 'Next player: ' + (this.state.xIsNext ? 'X' : 'O');

    // const winner = calculateWinner(this.state.squares);
    // let status;
    // if(winner) {
    //   status = 'winner: ' + winner;
    // }else {
    //   status = 'Next player: ' + (this.state.xIsNext ? 'X' : 'O');
    // }

    return (
      <div>
        {/* <div className="status">{status}</div> */}
        <div className="board-row">
          { this.renderSquare(0) }
          { this.renderSquare(1) }
          { this.renderSquare(2) }
        </div>
        <div className="board-row">
          { this.renderSquare(3) }
          { this.renderSquare(4) }
          { this.renderSquare(5) }
        </div>
        <div className="board-row">
          { this.renderSquare(6) }
          { this.renderSquare(7) }
          { this.renderSquare(8) }
        </div>
      </div>
    );
  }
}

class Game extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      history: [{
        squares: Array(9).fill(null)
      }],
      stepNumber: 0,
      xIsNext: true
    }
  }

  handleClick(i) {
    /**
     * 使用 .slice() 方法创建了数组的一个副本，而不是直接修改现有的数组
    */
    const history = this.state.history.slice(0, this.state.stepNumber + 1);
    const current = history[history.length - 1];
    const squares = current.squares.slice();
    if(calculateWinner(squares) || squares[i]) {
      return;
    }
    squares[i] = this.state.xIsNext ? 'X' : 'O';
    this.setState({ 
      history: history.concat([{
        squares: squares,
      }]),
      stepNumber: history.length,
      xIsNext: !this.state.xIsNext
    });
  }

  jumpTo(step) {
    this.setState({
      stepNumber: step,
      xIsNext: (step % 2) === 0
    })
  }

  render() {
    const history = this.state.history;
    const current = history[this.state.stepNumber];
    const winner = calculateWinner(current.squares);

    const moves = history.map((step, move) => {
      const desc = move ? 'go to move #' + move : 'go to game start';
      return (
        <li key={move}>
          <button onClick={() => this.jumpTo(move)}>{desc}</button>
        </li>
      )
    })

    let status;
    if(winner) {
      status = 'winner: ' + winner;
    }else {
      status = 'Next player: ' + (this.state.xIsNext ? 'X' : 'O');
    }
    return (
      <div className="game">
        <div className="game-board">
          <Board 
            squares={current.squares}
            onClick={(i) => this.handleClick(i)}
          />
        </div>
        <div className="game-info">
          <div>{status}</div>
          <ol>{moves}</ol>
        </div>
      </div>
    );
  }
}

// ========================================

ReactDOM.render(
  <Game />,
  document.getElementById('root')
);

function calculateWinner(squares) {
  const lines = [
    [0, 1, 2],
    [3, 4, 5],
    [6, 7, 8],
    [0, 3, 6],
    [1, 4, 7],
    [2, 5, 8],
    [0, 4, 8],
    [2, 4, 6],
  ];
  for (let i = 0; i < lines.length; i++) {
    const [a, b, c] = lines[i];
    if (squares[a] && squares[a] === squares[b] && squares[a] === squares[c]) {
      return squares[a];
    }
  }
  return null;
}
